Surveillance Testing for Influenza Virus

Public Health in the National News – During the recent government shutdown, news media frequently mentioned that the Centers for Disease Control and Prevention (CDC) had stopped surveillance testing for the influenza virus. What is surveillance testing and why is tracking influenza outbreaks important? The Nebraska Public Health Lab’s assistant director, Anthony Sambol, and state training coordinator, Karen Stiles, help shed some light on the process recommended by the CDC.

The Nebraska Department of Health and Human Services Office of Epidemiology has had a comprehensive, statewide influenza surveillance testing system in place since 1999. This system actively tracks the type and incidence of influenza infections in our state. When a patient is diagnosed by the Rapid Influenza Detection Test as having an influenza virus type “A” or “B” or other influenza-like illness under the state surveillance program, the specimen is sent to the Nebraska Public Health Laboratory (NPHL), located in the Department of Pathology and Microbiology at the University of Nebraska Medical Center, for further testing and confirmation. If the sample is confirmed positive at the NPHL by methodologies provided by the CDC, the NPHL sends the sample to the CDC for further antiviral susceptibility testing as well as strain characterization. This process is followed by other states as well.

The surveillance system is important because it provides real-time data on the prevalence of influenza within Nebraska, allowing health officials to issue reminders about getting vaccinated as well as social distancing and treatment if an individual is infected. The data is also important on several levels as it provides information on the target group that is coming down with the most cases of influenza, the virulence of the disease strain, the course of the disease within the state, and the efficacy of the vaccine for the general population.

Additionally, not all strains of influenza virus can be treated with the same antiviral medication. The data can be used to make recommendations on where shipments of influenza vaccine should be delivered and the age group targeted for vaccination, so the most affected communities receive increased numbers of doses to be used.

Besides surveillance on a state level, the CDC tracks influenza infections on a national level. They monitor for the different strains of influenza circulating in the environment as well as the antiviral patterns seen in these strains. By doing this type of surveillance, the CDC can send out information to all health care providers, as well as the general public, about how the influenza season is progressing, the need to continue to get vaccinations, and the use of antiviral medication that can be taken to help alleviate symptoms if infected with influenza.

The importance of surveillance testing of influenza virus was demonstrated in the May 2009 outbreak of a new strain of Influenza A, H1N1, that occurred first in Mexico and then spread rapidly in the United States and the rest of the world. Without the CDC surveillance system, people would have had no medical guidance to help fight the diseases. To read more about this topic, please go to http://www.cdc.gov/flu/index.htm